This proposal is for pilot studies leading to crystallization and structure determination by x-ray diffraction of protein isoaspartyl methyltransferase (PIMT. PIMT catalyzes a process for reparing proteins which have been damaged by a specific spontanious mechanism. This mechanism converts the normal asparagine residues of proteins into either aspartic acid residues or abnormal isoaspartyl residues. By transferring a methyl group to the abnormal residue, PIMT initiates a repair pathway for these damaged proteins. The importance of this pathway is suggested by its prevalence and conservation throughout the bioligical world. Proteins damaged by isoaspartyl formation accumulate with age and have been associated with several disease conditions. Structure determination of the PIMT enzyme will enhance our understanding of this process and perhaps allow us to design better enzymes for diagnostic and therapeutic purposes.